Method for the manufacture of collagen tape



y 12, 1,970 1 E- J. GRISET, JR 3,511,904 I METHOD FOR THE MANUFACTURE OFCOLLAGEN TAPE Filed Nov. 16, 1967 INVENTOR fPA/zsr d. 679/557 JR.

ATTORNEY United States Patent O 3,511,904 METHOD FOR THE MANUFACTURE OFCOLLAGEN TAPE Ernest J. Griset, Jr., Bound Brook, N.J., assignor toEthicon, Inc., a corporation of New Jersey Filed Nov. 16, 1967, Ser. No.683,505 Int. Cl. D01f 9/04 US. Cl. 264202 4 Claims ABSTRACT OF THEDISCLOSURE In the manufacture of a collagen tape which may be twisted toform a round strand that is useful as an absorbable surgical suture, anacid dispersion of collagen fibrils is extruded into a dehydrating bathto form a multifilament. The multifilament, while still wet from thedehydrating bath, is compressed and stretched to form a ribbon-like tapein two or more steps by passage between two or more sets of squeezerolls, the space between succeeding sets of rolls decreasing so that thecompression of the multifilament is accomplished in two or moreincrements. A certain amount of stretch is imparted to the tape as itpasses between the sets of squeeze rolls to assist in the orientation ofthe collagen fibrils. By varying the total compression and stretching ofthe wet multifilament, the width and thickness of the tape can becontrolled.

BACKGROUND OF THE INVENTION This invention relates to strand-likematerials, such as absorbable sutures and ligatures, made from collagenfibrils. More specifically, the present invention is an improvement inthe method of producing a collagen strand as described in United StatesPat. No. 3,114,593.

The aforesaid patent describes the continuous extrusion of a homogeneousdispersion of pure swollen collagen fibrils into a dehydrating bath toform a bonded multifilament tape that is further processed, for example,by tanning, twisting, and stretching in proper sequence to obtain around strand of uniform diameter and physical properties having utilityas an absorbable suture. The method for manufacturing a continuouslength of a ribbon-like collagen tape wherein the individual filamentsthat make up the tape cohere together to form a unitary structure isdescribed in Example X and is illustrated in FIG. 28 of Pat. No.3,114,593.

It is a disadvantage of the manufacturing process described that precisecontrol of the width and thickness of the tape is difficult to achieve,and variations in excess of ten percent in these dimensions may beexperienced. Such variations have a profound effect on tannagepenetration which is dependent on the relationship of the surface areato volume. Variations in the width and thickness of the tape alsoeffects the roundness and coherence of the finished strand, which isdependent on the number of turns that are required to roll the flat tapeinto the finished round string.

Another problem that may occur in the manufacturing process illustratedin FIG. 28 of Pat. No. 3,114,593 relates to the control of the flow ofair through the drying chamber. If the tape within the drying chamber 66is too wet, an attempt to correct this situation by increasing the airflow can cause folding of the tape and inordinately high tape tensionthat may cause the tape to break.

It is an advantage of the improved process to be described that precisecontrol of tape tension during spinning can be maintained.

It is another advantage of the improved process to be described thatprecise control of tape dimensions can be maintained.

It is an additional advantage of the improved process to be describedthat the tape production speed can be increased.

It is an additional advantage of the improved process to be describedthat it permits the manufacture of a thinner, wider tape than could beobtained by the process described in U. S. Pat. No. 3,114,593.

It is an additional advantage of the improved process to be describedthat it practically eliminates breakage of the tape during thestretching procedure.

SUMMARY OF THE INVENTION In accordance with the present invention, theextruded collagen multifilament is passed between a first driven godetand a first squeeze roll and compressed to form a ribbon-like tape, theamount of compression being controlled by the space between the drivengodet and squeeze roll. The resultant wet tape is then passed to asecond driven godet and a second squeeze roll with some stretching toassist in orienting the collagen fibrils, where it is again compressedby virtue of the space between the second driven godet and secondsqueeze roll being less than the space between the first godet and firstsqueeze roll. The distance that the tape travels between the first andsecond squeeze rolls efiects the tape tension between these two points.

This procss of compressing and stretching the tape may be repeated asoften as desired. The end product is a well-bonded, wet tape consistingof highly-oriented, partially swollen collagen fibrils and containingessentially no free fluid. Final drying of the tape to equilibrium withambient relative humidity is accomplished by passing the tape many timesbetween a driven godet and an idler roll. The dried tape is thencollected continuously on a take-up drum (spool). In this manner, a tapeof the desired width and thickness, consisting of highly-orientedcollagen fibrils, is produced with essentially no machine down time dueto breakage.

For a more complete understanding of the invention, reference should bemade to the accompanying drawing which illustrates a method ofcontinuously squeezing and stretching an extruded collagen tape as it istransported from the dehydrating bath to a take-up drum.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic view of amachine that may be used to manufacture a collagen tape and illustratesthe physical handling steps and the apparatus employed.

With specific reference to the drawing, a wet, extruded collagenmultifilament 8 passes from the dehydrating bath 10 and over the drivengodet 14. A squeeze roller 16 in rolling contact with the godet 14flattens the wet multifilament by a controlled amount and removes excessliquid therefrom. The wet multifilament in passing over the godet 14under the pressure of the roller 16 is bonded together to form aribbon-like tape. The tape from the godet 14 passes around the idlerroller 18 and over the driven godet 20 which rotates more rapidly thenthe godet 14 stretching the tape. The tape is again compressed by acontrolled amount as it passes over the godet 20 by a second squeezeroller 22 which removes additional liquid from the tape. The process ofalternately compressing and stretching the tape may be repeated as oftenas desired. If only the first and second squeeze rollers are used, thetape from the godet 20 passes around the idler roller 24 and is furtherair dried between the driven godet 26 and godet 28, being continuouslycollected on the take-up drum 30.

The stretch that is applied between the godets 14 and 20 will dependupon their relative peripheral speeds. Thus, if the peripheral speed ofthe godet 20 is 7.5 percent greater than the peripheral speed of thegodet 14, a 7 /2 percent stretch will be applied between these twogodets. In a similar manner, further stretching of the moving collagentape can be obtained between godet 20 and 26 by increasing theperipheral speed of the godet 26. It will be obvious that a difierentialstretch is applied to the tape by increasing the peripheral speed ofsuccessive godets and that this may be accomplished by either increasingthe diameter of successive godets, increasing the angular velocity ofrotation of successive godets, or increasing both the diameter andangular velocity.

It has been discovered that movement of the idler 18 upwardly todecrease the distance traveled by the tape between godets 14 and 20increases the tape tension at the idlers 18 and 24, and that themovement of the idler 18 downwardly to increase the distance traveled bythe tape between godets 14 and 20 decreases the tape tension in bothzones. Likewise, movement of the idler 24 vertically upward to shortenthe tape travel will increase the tape tension; and when moved down toincrease the tape, travel will decrease the tape tension. Movement ofthe idler 24, however, affects only the tension on the tape between thegodet 20 and 26 and does not change the tape tension between godet 20and 14.

By vertical movement of the idlers 18 and 24, therefore (either up ordown), one may control the tape tension to avoid breaking the tape evenunder conditions imparting a high degree of stretch thereto.

DESCRIPTION OF THE PREFERRED- EMBODIMENT Example I A dispersion ofacid-swollen collagen fibrils in an aqueous methanol cyanoacetic acidsolution is prepared as described in Example X of Pat. No. 3,114,593.This collagen dispersion is extruded through a stainless steelspinnerette, drilled with 192 openings arranged in concentric circlesinto an acetone dehydrating bath containing 130 mg. of ammonia and 50 g.of water per liter. The extruded multifilament is squeezed a controlledamount by adjusting the clearance between the driven godet 14 and thesqueeze roller 16 to remove excess acetone and ammonia and compress andbond the individual filaments into a unitary ribbon-like tape. Thecollagen tape from the godet 14 passes around the idler roller 18 and issqueezed by a controlled amount between the driven godet 20 and a secondsqueeze roller 22, which presses additional liquid from the tape andreduces the thickness of the collagen tape. The godet 20 is of the samediameter as godet 14 but rotates at an angular velocity that is 7%percent greater than that of godet 14 thereby producing the stretch of 7/2 percent in the collagen tape as it moves between the godet 14 and thegodet 20. The position of the idler 18 is such that the tension on thetape in the zone between godets 14 and 20 is 135 g. Additional stretchis applied to the collagen tape as it moves between the godets 20 and26, the idler 24 being positioned so that the tape tension in this zoneis 200 g. The amount of stretch as the tape passes between godets 20 and26 is 15.5 percent. Thus a 4 total stretch of about 23 percent isapplied to that length of tape that is moving between the godets 14 and26.

The stretched collagen tape is air dried as it moves over the rollers18, 24, and passes between the driven godet 26 and the idler roller 28.The product is collected in its dry state at equilibrium with ambientrelative humidity on the take-up drum 30. The collagen tape collected onthe take-up drum 30 is about mils in width and about 3 mils inthickness. It may be processed as described in Example XI of Pat. No.3,114,593 to obtain a collagen strand that has a diameter of 15.0 mils(1270 denier), a dry tensile strength of 4.2 grams per denier, a dryknot strength of 2.3 grams per denier, and a wet knot strength of 1.35grams per denier.

A thin cross-section of this strand upon microscopic examinationresembles the strand prepared in accordance with Example XI of US. Pat.No. 3,114,593 in that it resembles a jelly roll, the collagen ribbon ortape being rolled upon itself. Because the tape is thinner and widerthan the tape prepared in accordance with Example X of theabove-mentioned patent, however, there are more convolutions of the tapethat form the strand.

Example II The method of Example I is repeated, but the tape isstretched 19.5 percent between godets 14 and 20 and 10.5 percent betweengodets 20 and 26. The tension in the first stretching zone is adjustedto 30 grams by movement of the idler 18 and the tension in the secondstretching zone is adjusted to grams by movement of the idler 24.

Example III The method of Example I is repeated, but the tape isstretched 23 percent between godets 14 and 20 and 12 percent betweengodets 20 and 26. The tension in the first stretching zone is adjustedto 50 grams by movement of the idler 18 and the tension in the secondstretching zone is adjusted to 200 grams by movement of the idler 24.

It should be understood that the above description has been made withreference to the preferred embodiment illustrated in the drawing andthat modification and alterations can be made therein without departingfrom the invention, except as expressly limited hereafter in the claims.

What is claimed is:

1. In the manufacture of a collagen tape by the continuous extrusion ofan acid dispersion of collagen fibrils to form a multifilament whereinthe multifilament is passed between a driven godet and a first squeezeroller to form a ribbon-like tape in which the individual filamentscohere and the tape is stretched while wet and dried, the improvementwhich comprises:

stretching the tape as it passes between said first squeeze roller and asecond squeeze roller and controlling the tape tension by adjusting thedistance that the tape travels between said first and second squeezeroller.

2. The method of claim 1, wherein said tape is stretched a second'timeafter it leaves the second squeeze roller.

3. In the manufacture of a collagen tape by the continuous extrusion ofan acid dispersion of collagen fibrils into a dehydrating bath to form amultifilament wherein the :multifilarnent as it leaves the dehydratingbath is passed between a driven godet and a first squeeze roller to forma ribbon-like tape in which the individual filaments cohere and the tapeis stretched while wet and dried, the improvement which comprises:

stretching the tape as it passes between said first squeeze roller and asecond squeeze roller and imparting additional stretch to the tape as itmoves away from the second squeeze roller by contacting the tape with agodet, which revolves in the direction that the tape 5 6 is moving at aperipheral speed greater than that of 3,114,591 12/1963 Nichols et al264-202 X the second squeeze roller. 3,259,681 7/1966 Bullet a1. 4. Themethod of claim 3, wherein the tape tension is 3,389,206 6/1968 Jamieson264-34l X controlled in each stretching zone by varying the distancethat the tape travels in moving through that zone. 5 FOREIGN PATENTS1,117,038 5/1956 France. References Cited 163,803 7/ 1955 Australia.

UNITED STATES PATENTS JULIUS FROME, Primary Examiner Mummery. 15

